Work machines such as material handling machines for use at construction sites typically have large diameter front and rear wheels driven by a power train. These material handling machines are designed to carry out given tasks such as digging, loading, or pallet-lifting. The relatively large wheels place a constraint on the arrangement of the machine's power train components and operator's cabin.
One known material handling machine for use at construction sites is a telescopic handler. This machine has an elongated main frame defined by first and second substantially parallel and vertically oriented side members that are spaced apart to form a longitudinally extending gap centered about a longitudinal vertical center plane of the material handling machine. A boom is pivotally connected at one end of the boom to a back end portion of the main frame and extends parallel to the center plane of the material handling machine so that a second end of the boom passes a front end portion of the main frame. The boom may have an implement mounted at its second end for performing an intended work function. An operator's cabin is typically located to one side of the boom, while the engine, cooling system, and transmission are located to a second side of the boom. The above configuration generally provides good operator visibility in all directions, except the direction in which the engine, cooling system, and transmission obstruct the operator's visibility.
In the known material handling machine, such as the telescopic handler described above, the cooling system, engine, and transmission are mounted serially in that order to the main frame. That is, the engine is disposed between the transmission and the cooling system. In the case of a four wheel drive system, the material handling machine further includes front and rear axles mounted beneath the main frame to complete the power train to wheels that are carried by the front and rear axles. A front differential couples the front axle to a first drive shaft, and a rear differential couples the rear axle to a second drive shaft. Both first and second drive shafts extend longitudinally beneath the longitudinally extending gap formed by the side members of the main frame. Hydraulically actuated piston-cylinder devices may be used to steer the wheels.
Since the engine is arranged outside the longitudinal vertical center plane of the material handling machine and is elevated with respect to the machine's differentials, the transmission, which can include a reducing transmission, is required to overcome significant vertical and lateral distances in order to transmit torque from the engine to the differentials. As a result, severe drive shaft angles are created that can cause vibration and wear in the power train. Additionally, the larger the material handling machine, the more severe the drive shaft angles can be, since the main frames are wider on the larger machines. Therefore, different cooling system, engine, and transmission designs are required for different size machines to adapt to the different sizes of the main frames.
Furthermore, since the engine is arranged between the transmission and cooling system, the weight of the engine cannot be effectively used as a counter weight against a load at the front end of the material handling machine, such as a load carried by the boom in the case of a telescopic handler.
For example, U.S. Pat. No. 6,105,710 discloses a material handling machine in which an engine is arranged outside the longitudinal center plane of the machine, and a transmission is coupled to one end of the engine through a torque converter at one end of the engine opposite to where the cooling system is connected. The transmission includes a reducing transmission coupled to an output shaft of the engine for reducing the number of revolutions of the engine's output shaft, and a transfer transmission that takes an output torque from the reducing transmission and transmits this torque to the drive shafts.
Since the transmission disclosed in U.S. Pat. No. 6,105,710 is coupled to one end of the engine at a side of the engine opposite to where the cooling system is connected, the transmission is coupled to the drive shafts at a position off-center with respect to the front and rear differentials. Consequently, one of the drive shafts is shorter than the other, resulting in a severe drive shaft angle for at least the shorter shaft. Furthermore, since the engine is disposed forward of the transmission, the engine's weight cannot be effectively used as a counter weight against a load at the front end of the material handling machine, such as a load carried by the boom in the case of a telescopic handler.
Additionally, U.S. Pat. No. 6,152,253 discloses a drive train arrangement for a construction vehicle wherein a side frame member extends laterally from a central frame member of the vehicle and defines a drive train receiving space for an engine, transmission and transfer case. The engine and transmission are oriented in a side-by-side configuration and connected via the transfer case such that the transmission input and output extend along an axis coincident with the longitudinal axis of the central frame member.
Due to the positioning of the transmission along an axis coincident with the longitudinal axis of the central frame member, the transfer case is disposed in a manner that laterally offsets the engine and the transmission. The positioning of the drive train components in this manner limits loading and spacing advantages available on the vehicle and ignores valuable and efficient connecting relationships between the components.
The present invention is directed to overcoming one or more of the problems as set forth above.